High-frequency composite switch component

ABSTRACT

The present invention relates to a hybrid radio frequency (RF) switching device. It is an object of the invention to provide a hybrid RF switching device including fewer diodes and having a smaller size and high performance. To achieve the object according to the invention, the device includes first to fourth ports, a diode coupled between the first port and second port, a first transmission line having a length of λg/4 (where λg is a wave length of a frequency in a first frequency band), and a first element coupled in series with the first transmission line having an almost simple reactance component and nearly opening in a second frequency band. The first transmission line and first element are coupled in series between the second port and third port. The device further includes a second transmission line having a length of λd/4 (where λd is a wavelength of a frequency in the second frequency band), and a second element having an almost simple reactance component and nearly opening in the first frequency band. The second transmission line and second element are coupled in series between the second port and fourth port.

FIELD OF THE INVENTION

[0001] The present invention relates to a radio frequency (RF) switchingdevice, which is provided mainly in a mobile communication apparatussuch as mobile phone, in which a switching circuit for switching betweena transmitting and a receiving and a branching circuit for branchingdifferent transmitting/receiving bands, a low-pass filter at thetransmitting side, and a band pass filter at the receiving side arehybridized.

BACKGROUND OF THE INVENTION

[0002] Recently, a switch duplexer having a small size and highperformance is demanded increasingly for use in mobile phone. Aconventional circuit configuration of an conventional switch duplexerfor dual bands is shown in FIG. 14. A circuit configuration of theswitch duplexer in a composite terminal for mobile phone systems calledGSM in a 900 MHz band and DCS in a 1.8 GHz band, both of which are inservice in Europe at present time.

[0003] In the diagram, reference numerals 1001 to 1005 denoteinput/output ports, reference numerals 1006 and 1007 denote controlterminals, reference numerals 1008 to 1011 denote diodes, referencenumerals 1012 and 1013 denote transmission lines, reference numerals1014 and 1015 denote band-pass filters (BPFs), and reference numeral1016 denotes a diplexer. Diplexer 1016 is generally composed of circuitscombined with low-pass filter (LPF) 1016 a and high-pass filter (HPF)1016 b.

[0004] In this circuit configuration, an antenna (not shown) isconnected to input/output port 1005, and the signal received by theantenna is first distributed into GSM signal and DCS signal by diplexer1016. The length of transmission lines 1012 and 1013 are set atone-quarter wavelength for the frequency bands of GSM and DCS,respectively. When a positive voltage is applied to the control terminal1006 where a current flows accordingly, diodes 1008 and 1010 are turnedon, and ports 1005 and 1001 are thus coupled each other. Similarly, whena positive voltage is applied to the control terminal 1007 where acurrent flows accordingly, diodes 1009 and 1011 are turned on, and ports1005 and 1003 are thus coupled. If a voltage is not applied to controlterminals 1006 or 1007, diodes 1008 to 1011 are turned off, and ports1005 and 1002 are thus disconnected, and ports 1005 and 1004 are thusdisconnected.

[0005] Ports 1001 and 1003 operate as transmission ports (Tx). BPFs 1014and 1015 operates as filters for limiting a receiving bandwidth. Ports1002 and 1004 operates as reception ports (Rx).

[0006] In such conventional configuration, four diodes are required.Since having larger sizes than other circuit components such as L and C,the diodes have not been integrated into a laminated body, and thus thedevice is hardly reduced in size. The diodes are more expensive than theother circuit components and thus increases the cost of the device.Besides, the switch duplexer for both GSM and DCS requires a couple oftransmission lines 1012 and 1013, which also have the duplexer hardlyreduced in size.

SUMMARY OF THE INVENTION

[0007] The invention is intended to solve the problem, and it is hencean object thereof to provide a hybrid radio frequency (RF) switchingdevice with a small size and high performance which including fewerdiodes.

[0008] To achieve the object, the device of the invention includes:

[0009] first to fourth ports;

[0010] a diode connected between the first and second ports,

[0011] a first transmission line having a line length of λg/4×n, λgbeing a wavelength of a frequency in the first frequency band, n beingan odd number of 1 or larger;

[0012] a first element coupled between the second and third ports inseries with the first element, the first element having an impedancecontaining a nearly simple reactance component at the second frequencyband;

[0013] a second element coupled at a coupling position where the firstelement having a nearly open impedance at the second frequency band, thesecond element having an impedance containing a nearly simple reactancecomponent; and

[0014] a reactance circuit or a second transmission line, the reactancecircuit being coupled in parallel with the second element, the secondtransmission line being coupled in series with the second element, thesecond element having an open impedance as seen from the couplingposition at the first frequency band. That provides a small-sized hybridRF switching device having a simple structure and exhibiting a highperformance

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a circuit diagram of a hybrid radio frequency (RF)switching device according to embodiment 1 of the present invention.

[0016]FIG. 2 is a circuit diagram of a surface acoustic wave (SAW)filter according to the embodiment.

[0017]FIG. 3 is a characteristic diagram of an isolation between inputand output ports according to the embodiment.

[0018]FIG. 4 is a circuit block diagram showing a schematicconfiguration of a hybrid RF switching device according to embodiment 2of the present invention.

[0019]FIG. 5 is a specific circuit configuration of the block diagramshown in FIG. 4.

[0020]FIG. 6 is another specific circuit configuration of the blockdiagram shown in FIG. 4 according to embodiment 3 of the presentinvention..

[0021]FIG. 7 is further specific circuit configuration of the blockdiagram shown in FIG. 4 according to embodiment 4 of the presentinvention.

[0022]FIG. 8 is a circuit block diagram showing a schematicconfiguration of a hybrid RF switching device according to embodiment 5of the present invention.

[0023]FIG. 9 is a specific circuit configuration of the block diagramshown in FIG. 8 according to embodiment 5 of the present invention.

[0024]FIG. 10 is a circuit block diagram showing a schematicconfiguration of a hybrid RF switching device according to embodiment 6of the present invention.

[0025]FIG. 11 is a specific circuit configuration of the block diagramshown in FIG. 10.

[0026]FIG. 12 is a perspective view showing a schematic configuration ofa hybrid RF switching device according to embodiment 7 of the presentinvention.

[0027]FIG. 13 is a perspective exploded view of the device according tothe embodiment.

[0028]FIG. 14 is a circuit block diagram showing a schematicconfiguration of a conventional switch duplexer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

[0029] Embodiment 1 of the present invention will be explained belowwhile referring to accompanying drawings.

[0030]FIG. 1 is a circuit diagram of a hybrid radio frequency (RF)switching device according to embodiment 1 of the invention. Referencenumerals 101, 102, 103, and 104 denote input/output ports. Referencenumeral 105 denotes a control terminal. Reference numerals 106 denotes adiode. Reference numerals 107, 108, and 113 denote transmission lines.Reference numerals 109 and 110 denote surface acoustic wave (SAW)filters. Reference numerals 111, 115, and 116 denote inductors.Reference numerals 112, 114, and 117 denote capacitors, and referencenumeral 118 denotes a branching circuit.

[0031] In this embodiment, for an easily-understandable explanation,frequencies are defined as follows.

[0032] A signal component from the port 101 to the port 102: 880-915 MHzand 1710-1785 MHz (hereinafter called transmission bands)

[0033] A signal component from the port 102 to the port 104: 925-960 MHz(hereinafter called a first reception band)

[0034] A signal component from the port 102 to the port 103: 1805-1880MHz (hereinafter called a second reception band)

[0035] A frequency in the second reception band is about twice thepass-band band frequency of the SAW filter 110, and hence the absolutevalue of a reflection coefficient at the input terminal of the SAWfilter 110 is close to 1. Accordingly, in this embodiment, thetransmission line 108 is connected, and the impedance from a point Atoward the left side in the diagram in the second band is set to anearly open.

[0036] A frequency in the first reception band is about a half of thatof a pass band of the SAW filter 109, and hence the absolute value of areflection coefficient at the input terminal of the SAW filter 109 isclose to 1. Accordingly, in this embodiment, transmission line 113, aninductor 111 and capacitor 112 are connected as shown in the diagram,the impedance from a point B toward the bottom side in the diagram inthe first band is set to a nearly open.

[0037] In other words, a composite impedance of the inductor 111 andcapacitor 112 in the first band and an impedance from a point B′ towardthe bottom side in the diagram in the first band parallel-resonate.Further, as a technique for avoiding an adverse influence on thepass-band characteristic in the second band, herein, the inductor 111and capacitor 112 parallel-resonating in the second band are employed.

[0038] In such configuration, a circuit block 118 operates as abranching circuit. Further, the SAW filters 109 and 110 present a steepattenuation characteristic.

[0039]FIG. 2 is a circuit configuration diagram of the SAW filter inFIG. 1. Reference numeral 121 denotes an input terminal. Referencenumeral 122 denotes an output terminal. Reference numerals 123 to 126denote resonance elements of the SAW filter. In the SAW filters 109 and110 in Fig.1, the first resonance element is connected in shunt to aground at the input terminal as shown in FIG. 2, and thus, an inputimpedance at input terminal 121 becomes a short-circuit in thetransmission band.

[0040] Referring to FIG. 1, when transmitting by turning on diode 106,it is preferable that an impedance from a point C toward the right sideis set to an open-circuit in the transmission band. For this purpose, inthis embodiment, a total line length of transmission lines 107 and 108is set to λg/4 at a frequency in 880-915 MHz band, where λg is awavelength corresponding to the frequency. On the other hand, asexplained above, an impedance from a point B toward bottom side is setto a nearly open-circuit, and thus the circuit operates preferably inthe 880-915 MHz band.

[0041] An impedance from a point A toward the right side is set to anearly open-circuit by the same reason. A total line length oftransmission lines 107 and 113 of λd/4 at a frequency in a 1710-1785 MHzband, where λd is a wavelength corresponding to the frequency, providesan impedance from a point C toward the right side in the diagram with anearly open-circuit in a 1710-1785 MHz band. And ports 101 and 102 areaccordingly coupled.

[0042] In the embodiment, transmission line 113 may be either atransmission line having a positive length or a transmission line havinga negative length. The transmission line having the negative length canbe equivalently provided by a π-form or T-form circuit (a high passfilter) in which an inductor is connected in shunt, and a capacitorconnected in series.

[0043] The transmission lines 107, 108, and 113 may be converted into anequivalent lumped constant circuit, instead of distributed constantcircuit such as transmission lines. In such a case, the circuitincluding the inductor 111 and capacitor 112 can be combined andsimplified, and the dimension of the circuit can be reduced.

[0044] Further, a circuit composed of the inductors 115, 116 andcapacitor 114 can parallel-resonate together with a capacitance betweenthe terminals of the diode 106 where a current is turned off in thefirst and second reception band. Therefore, an isolation between theports 101 and 102 is assured when the current is turned off and canreduce the adverse influence to other pass-band characteristics.

[0045]FIG. 3 shows an isolation characteristic between the ports 101 and102 under a condition that the capacity between the terminals of thediode 106 is about 0.27 pF, and the values of the inductors 115, 116 andcapacitors 114, 117 are 12 nH, 39 nH, 1.9 pF, and 15 pF, respectively.That provides a more favorable characteristic than the case of the diode106 alone.

[0046] The transmission line 107 consists of a microstrip line, a stripline, or an equivalent circuit consisting of a capacitor connected inshunt and an inductor connected in series. And the inductor 111connected as shown in the diagram guides the current flowing out fromthe control terminal 105 to the ground, and has any particular chokeinductor connected to the ground unnecessary.

[0047] The circuit shown in FIG. 1 can be formed into a laminated bodyhaving plural dielectric sheets. At the moment, the diode 106 and SAWfilters 109 and 110 can be mounted on the laminated body, and thetransmission lines 107, 108, and 113, inductors 111, 115, and 116, andcapacitors 112, 114, and 117 can be formed in the laminated body. Then,circuit dimensions can be substantially reduced as compared with a flatstructure forming the same circuit on a substrate.

[0048] Thus, according to the embodiment, the circuit includes only onediode. Contrary to a circuit having four large, expensive diodesrequired in the prior art, a small, inexpensive hybrid RF switchingdevice can be provided. A part of the circuit of this hybrid RFswitching device can be used as a branching circuit. Moreover, a circuitcoupled to the port 101 for combining and branching signals in 900 MHzband and 1.8 GHz band provides transmission ports for the respectivebands.

Embodiment 2

[0049] Embodiment 2 of the invention will be explained below byreferring to the drawings.

[0050]FIG. 4 is a block diagram showing a schematic configuration of ahybrid radio frequency (RF) switching device according to embodiment 2of the present invention.

[0051] In this embodiment, an input/output port 1 is a common port forinputting and outputting an RF signal. A frequency is set as follows.

[0052] A signal component delivered from an input/output port 2 to theport 1: 880-915 MHz (hereinafter called a first transmission band)

[0053] A signal component delivered from an input/output port 3 to theport 1: 1710-1785 MHz (hereinafter called a second transmission band)

[0054] A signal component delivered from the port 1 to an input/outputport 4: 925-960 MHz (hereinafter called a first reception band)

[0055] A signal component delivered from the port 1 to an input/outputport 5: 1805-1880 MH (hereinafter called a second reception band)

[0056] In FIG. 4, a switch 10 switches between a transmitting andreceiving. A transmission signal from the ports 2 and 3 are combined anddivided into the first and the second transmission bands in a diplexer9. Low-pass filters (LPFs) 7 and 8 are provided in respective routes. Atan receiving side, a signal is branched into the first and the secondreception bands by a diplexer 11 having a phase-shifting function.Surface acoustic wave (SAW) filters 13 and 12 are provided in respectiveroutes. The switch 10 is controlled through a control terminal 6.

[0057]FIG. 5 shows a specific circuit configuration of the block diagramin FIG. 4. In FIG. 5, reference numerals 14 to 29 denote capacitors,reference numerals 30 to 41 denote inductors, reference numeral 42denotes a current control resistor, and reference numeral 43 denotes adiode for composing the switch 10 in Fig.4. The capacitors 14 to 16 andinductor 30 compose the LPF 7, and the capacitors 21 and 22 andinductors 33 and 34 compose the LPF 8. The capacitors 16 to 19 andinductors 31 and 32 compose the diplexer 9. The capacitors 26 to 29 andinductors 38 to 41 compose the diplexer 11 with a phase shiftingfunction.

[0058] Component values are determined so that a parallel resonancecircuit consisting of the capacitor 17 and inductor 31 may resonatenearly in the second transmission band, and a series resonance circuitconsisting of the inductor 32 and capacitor 20 may resonate nearly inthe first transmission band.

[0059] Component values are determined so that a parallel resonancecircuit consisting of the capacitor 27 and inductor 39, and a parallelresonance circuit consisting of the capacitor 28 and inductor 40 mayresonate nearly in the first and second reception bands, respectively.

[0060] Each SAW filters 12 and 13 has an input impedance of a nearlyshort-circuit in each transmission band in a relation of frequenciesmentioned above. A phase rotation of the input impedance of each SAWfilters 12 and 13 can compose the switch 10 having an impedance from theport 1 toward the left side local-maximum.

[0061] That is, the capacitors 26 and 27 and inductors 38 and 39 operateas a phase shifter functioning equivalently as a T-form high-pass filterin the second reception band. Further, component values are determinedso that the SAW filter 12 may have the input impedance rotate on a Smithchart to have the impedance almost maximum in the second transmissionband.

[0062] On the other hand, the capacitors 28 and 29 and inductors 40 and41 similarly operate as a phase shifter functioning equivalently as aT-form high-pass filter in the first reception band. Further, componentvalues are determined so that the SAW filter 13 may have the inputimpedance rotate on a Smith chart to have the input impedance almostmaximum in the first transmission band.

[0063] In such configuration, in the first transmission band and secondtransmission band, since the impedance from the port 1 toward thereceiving circuit side is almost maximum, the switch 10 for switchingbetween a transmitting and receiving can be composed with the diode 43.

[0064] A circuit consisting of the capacitors 24 and 25 and inductors 36and 37 cancels the capacitance of the diode 43 turned off in the firstand second reception bands. The inductor 35 is a choke inductor, and thecapacitor 23 is a bypass capacitor.

[0065] The SAW filters 12 and 13, each particularly consisting of aladder-type filter as shown in FIG. 2, can steeply attenuate in avicinity of the pass-band. And each filter, upon particularly having ashunt resonator at an input stage, has a reflection coefficient of whichabsolute value is close to 1, so that it is more preferable.

[0066] That is, a resonance element 123 at the first stage placedclosely at the input terminal 121 is connected in shunt to the ground,and has the series resonance frequency set in the transmission band orthe vicinity. Therefore, the input impedance at input terminal 121 isset almost to a short-circuit in both the first and second transmissionbands.

[0067] Therefore, in FIG. 5, during a transmitting with the diode 43turned on, an impedance from a point A toward the right side in eachtransmission band may be set at an open-circuit. Accordingly, in thisembodiment, the T-form circuit consisting of the inductors 40 and 41 andcapacitors 28 and 29 has an equivalent electric length of λg/4 at afrequency in the first transmission band, where λg is a wavelengthcorresponding to the frequency. According to this setting, the SAWfilter 13 has the input impedance set at a nearly short-circuit in thefirst transmission band. Therefore, an impedance from a point A towardthe right side in the first transmission band is set at an open-circuitby the reason explained above, so that a desired operation is realized.

[0068] In the second transmission band, similarly, the SAW filter 12 hasthe input impedance set at an almost short-circuit. The T-form circuitconsisting of the inductors 38 and 39 and capacitors 26 and 27, uponhaving the equivalent electric length of λd/4, makes an impedance from apoint A toward the right side in the diagram become a nearlyopen-circuit. (where λd is a wavelength corresponding to the frequency.)As a result, in the first and second transmission bands, the diode 43,upon being turned on, couples the port 2 with the port 1 or couples theport 3 with the port 1 without a signal leakage to the ports 4 and 5through the SAW filters 12 and 13.

[0069] According to this embodiment, the SAW filters 12 and 13 providesteep attenuation characteristics, and can function sufficiently even inthe present frequency relation.

[0070] Further, according to the embodiment, a current for switching thediode 43 is supplied from the control terminal 6 to the ground throughthe diode 43, inductors 39 and 38, that is, a current path isestablished, and therefore, a choke inductor or the like is notparticularly needed.

[0071] Instead of the T-form circuit consisting of the inductors 40, 41and capacitors 28, 29, and instead of the T-form circuit consisting ofthe inductors 38, 39 and capacitors 26, 27 in the embodiment, athree-element T-form or π-form phase shifter which is equivalentlyexpressed as an lumped constant circuit may be combined with adistributed constant circuit.

[0072] The circuit composed of the inductors 36, 37 and capacitor 24 mayparallel-resonate in the first and second reception bands together witha capacitance between the terminals of the diode 43 where a current isturned off. Thus, the circuit can isolate the port 1 and a point Bsecurely when the current is turned off, and reduce an adverse influenceto other pass-band characteristics.

[0073] For example, under the condition that the capacitance between theterminals of diode 43 is 0.4 pF, and the inductors 36, 37 and capacitors24, 25 are 12.26 nH, 27 nH, 1.52 pF, and 33 pF, respectively, anisolation characteristic between the port 1 and point B is shown in FIG.3. A more favorable characteristic is obtained as compared with the caseof the diode alone.

[0074] The circuit shown in FIG. 5 can be formed in a laminated bodyhaving plural dielectric sheets. At the moment, the diode 43 and SAWfilters 12, 13 can be mounted on the laminated body, and the inductorsand capacitors can be formed in the laminated body. And thus, they canbe composed integrally, and have circuit size much reduced as comparedwith a flat structure forming the same circuit on a substrate.

[0075] According to the embodiment, the circuit includes only one diode.Contrary to the circuit including four large, expensive diodes requiredin the prior art, a small, inexpensive hybrid RF switching device can beprovided.

Embodiment 3

[0076] Embodiment 3 of the present invention will be explained below byreferring to the drawings.

[0077] In embodiment 3, a circuit of embodiment 2 is partially modified,and thus, modified portion will be mainly explained. The same parts asin embodiment 2 are denoted by the same reference numerals, and theirexplanation is omitted.

[0078]FIG. 6 shows a specific circuit configuration of the block diagramof FIG. 4, similarly to embodiment 2. In the diagram, reference numerals50 to 53 denote inductors, and reference numerals 54 to 59 denotecapacitors. They form a diplexer 11 a as shown in FIG. 6.

[0079] In diplexer 11 a, a resonance frequency of a parallel circuitcomposed of inductor 50 and capacitor 55 is set to the secondtransmission band and second reception band or the vicinity. And aresonance frequency of a series circuit composed of inductor 52 andcapacitor 57 is set to the first transmission band and first receptionband or the vicinity. In the first transmission band, a phase shiftershifting a phase by λg/4 with a desired characteristic impedance(usually 50Ω) is formed in a π-form circuit between the SAW filter 13and the port 1. The π-form circuit includes C (the capacitor 56)-L (acombined impedance of the inductor 50 and capacitor 55)-C (the capacitor54). In the second transmission band, a phase shifter shifting a phaseby −λg/4 with a desired characteristic impedance (usually 50Ω) is formedin a circuit between the SAW filter 12 and the port 1. The circuitincludes C (the capacitor 56)-L (a combined impedance of the inductor 52and capacitor 57)-C (the capacitor 58)-L (the inductor 53)-C (thecapacitor 59). The inductor 51 is a choke inductor for feeding a controlcurrent to the diode 43.

[0080] According to this setting, as explained in embodiment 2 of theinvention, the SAW filter 13 has an input impedance set at ashort-circuit in the first transmission band, and the SAW filter 12 hasan impedance set at a short-circuit in the second transmission band.Therefore, an impedance from a point A toward the right side is set atan open-circuit in the first and second transmission bands, so that adesired operation of this embodiment may be provided.

[0081] In the embodiment, the circuit composed of the inductors 50 to 53and capacitors 54 to 59 may be equivalently provided by a distributedconstant circuit or may be partly combined with a distributed constantcircuit.

[0082] The SAW filters 12 and 13, each particularly consisting of aladder-type filter as shown in FIG. 2, can steeply attenuate a vicinityof the pass-band. And each filter, upon particularly having a shuntresonator at the first stage, has a reflection coefficient of whichabsolute value is close to 1, so that it is more preferable.

[0083] The circuit shown in FIG. 6 can be formed in a laminated bodyhaving plural dielectric sheets. At the moment, the diode 43 and SAWfilters 12 and 13 are mounted on the laminated body, and the inductorsand capacitors can be formed in the laminated body. And thus, they canbe composed integrally, and have circuit size much reduced as comparedwith a flat structure forming the same circuit on a substrate.

[0084] According to the embodiment, the circuit includes only one diode.Contrary to the circuit including four large, expensive diodes requiredin the prior art, a small, inexpensive hybrid radio frequency (RF)switching device can be provided.

Embodiment 4

[0085] Embodiment 4 of the invention will be explained below byreferring to the drawings.

[0086] In embodiment 4, a circuit of embodiment 2 is partly modified,and thus, modified portion will be mainly explained. The same parts asin embodiment 2 are denoted by the same reference numerals, and theexplanation is omitted.

[0087]FIG. 7 shows a specific circuit configuration of the block diagramof FIG. 4, similarly to embodiments 2 and 3. In the diagram, referencenumerals 60 and 61 denote diodes. Reference numerals 62 to 67 denoteinductors. Reference numerals 68 to 75 denote capacitors. They form adiplexer 11 b as shown in FIG. 6.

[0088] A basic operation of the diplexer 11 b is the same as thatexplained in embodiment 3 of the invention, and thus, omitted herein. Inthis embodiment, the diodes 60 and 61 are grounded with capacitor 68 and75. They consequently provides an ideal short-circuit when the diodes 60and 61 are turned on with a current through them. That is, the diodesturned on have inductive components, and thus the capacitors 68 and 75have capacitances selected so as to cancel the inductive components inthe first and second transmission bands, respectively. The inductors 62,66, and 67 are choke inductors.

[0089] According to this setting, as explained in embodiments 2 and 3 ofthe invention, the SAW filter 13 has an input impedance set at an almostshort-circuit in the first transmission band, and the SAW filter 12 hasan impedance set at an almost short-circuit in the second transmissionband. Therefore, an impedance from a point A toward the right sidebecome an open-circuit, so that a desired operation may be provided inthe first transmission band and second transmission band.

[0090] Circuit components other than the diodes 60 and 61 for composingthe diplexer 11 b may be equivalently provided by a distributed constantcircuit or a partial combination of a distributed constant circuit.

[0091] The circuit shown in FIG. 7 can be formed in a laminated bodyhaving plural dielectric sheets. At the moment, the diodes 43, 60 and 61and SAW filters 12 and 13 can be mounted on the laminated body, and theinductors and capacitors are formed in the laminated body. And thus,they can be composed integrally, and have circuit size much reduced ascompared with a flat structure forming the same circuit on a substrate.

[0092] According to the embodiment, the circuit includes three diodes.Contrary to the circuit including four large, expensive diodes requiredin the prior art, a small, inexpensive hybrid radio frequency (RF)switching device can be provided.

Embodiment 5

[0093] By applying the foregoing embodiments 2 to 4, a hybrid radiofrequency (RF) switching device applicable to triple bands including,for example, GSM (900 MHz)/DCS (1.8 GHz) in Europe and PCS (1.9 GHz) inthe U.S.

[0094]FIG. 8 is a block diagram showing a schematic configuration of ahybrid RF switching device according to embodiment 5 of the invention.The block diagram in FIG. 8 is a modified one in FIG. 4. The same partsare denoted by the same reference numerals, and the explanation isomitted.

[0095] The DCS (1.8 GHz) and PCS (1.9 GHz) are close to each other, andthus, signals in them are driven by a common power amplifier. Therefore,in the diagram shown in FIG. 8, for transmission, the device has twosystems, a DCS-PCS system and a GSM system. In a reception side, thedevice includes surface acoustic wave (SAW) filters 12 a, 12 b andtransmission lines 80 a, 80 b to function as a switch.

[0096] That is, a switch 10 a switches between transmission andreception. At a transmission side, signals in GSM and DCS-PCS bands arecombined by diplexer 9 a through low-pass filters (LPFs) 7 and 8 a,respectively. At a reception side, a diplexer 11 c having a phaseshifting function roughly branches a signal into the GSM band andDCS-PCS band. Then, a signal in the DCS-PCS band are branched into theDCS band and PCS band through the transmission lines 80 a, 80 b,respectively. The SAW filters 12 a, 12 b are provided in the signalpaths. The switch 10 a is controlled through a control terminal 6.

[0097]FIG. 9 shows a specific circuit configuration of the block diagramin FIG. 8. The circuit in FIG. 9, which is based on that in FIG. 7, hasbasically the same structure and just has different component values aredifferent. Therefore, the same parts are denoted by the same referencenumerals, and the explanation is omitted.

[0098] The circuit in FIG. 9 includes a further SAW filter, thetransmission lines 80 a and 80 b for branching a signal into thereception bands, DCS and PCS, and treat the second transmission band of1710-1910 MHz (hereinafter called a third transmission band), and thesecond reception band of 1805-1990 MHz (hereinafter called a thirdreception band), which differs from the circuit in FIG. 7

[0099] Reference numeral 12 a denotes a SAW filter for a DCS receptionband, and reference numeral 12 b denotes a SAW filters for a PCSreception band. In the DCS (1805-1880 MHz) reception band and the PCS(1930-1990 MHz) reception band, each transmission lines 80 a and 80 bhas an electric length setting an impedance from a point C toward theopposite side (i.e., toward the SAW filter 12 b in the DCS receptionband) to an open-circuit. Further, considering a phase rotation in thetransmission lines 80 a and 80 b, an impedance from a point A toward theright side is set to an open-circuit in the third transmission band.

[0100] In this configuration, a desired operation may be realized.

[0101] The circuit shown in FIG. 9 can be formed in a laminated bodyhaving plural dielectric sheets. At the moment, the diodes 43, 60 and 61and SAW filters 12 a, 12 b and 13 can be mounted on the laminated body,and the inductors and capacitors are formed in the laminated body. Andthus, they can be composed integrally and have circuit size much reducedas compared with a flat structure forming the same circuit on asubstrate.

[0102] According to the embodiment,, a hybrid RF switching deviceapplicable to triple bands can be provided which has a simple circuitconfiguration.

Embodiment 6

[0103] Embodiment 6 of the invention will be explained below byreferring to the drawings.

[0104]FIG. 10 is a block diagram of a hybrid radio frequency (RF)switching device according to embodiment 6 of the invention. Referencenumerals 201, 202, 203, 204, 205 a, and 205 b denote input/output ports.Reference numeral 207 and 208 denote low-pass filters (LPFs). Referencenumerals 212 a, 213 a, and 213 b denote surface acoustic wave (SAW)filters. Reference numerals 244 and 245 denote control terminals.Reference numeral 248 denotes a diplexer composed of an LPF andhigh-pass filter (HPF). Reference numerals 246 and 247 denote switches.Reference numerals 281 a, 281 b, and 281 c are transmission lines.

[0105] In the diagram, for transmission, signals in DCS (1.8 GHz) andPCS (1.9 GHz) bands which are close to each other are driven by a commonpower amplifier, and thus the device has two system, a DCS-PCS systemand GSM system. In a receiving side, the device has the SAW filters 213a and 213 b, and the transmission lines 281 a, 281 b and 281 c tofunction as a switch, and thus the device includes three systems, theGSM, DCS, and PCS systems.

[0106] That is, the diplexer 248 roughly branches and combines signalsinto a GSM band and DCS-PCS band. A signal in the GSM band is furtherbranched into the transmission band and reception band by the switch246. The LPF is connected at the transmission side, while the SAW filter212 is connected at the reception side.

[0107] The DCS-PCS band is also branched into the transmission band andthe reception band by the switch 247. The LPF 208 is coupled at thetransmission side, while the reception side is further branched into DCSand PCS bands through transmission lines 281 a, 281 b, and 281 c tofunction as switch. The SAW filters 213 a and 213 b are coupled inrespective paths. The switches 246 and 247 are controlled throughcontrol terminals 244 and 245.

[0108]FIG. 11 shows a specific circuit configuration of the blockdiagram in FIG. 10. In the diagram, reference numerals 249 to 263 denotecapacitors. Reference numerals 264 to 273 denote inductors. Referencenumerals 276 and 277 denote current control resistors. Reference numeral278 denotes a diode for composing the switch 246 in FIG. 10, andreference numeral 279 denotes a diode for composing the switch 247 inFIG. 10. Capacitors 249 to 251 and inductor 264 compose the LPF 207, andcapacitors 259 to 261 and inductor 270 compose the LPF 208. Further,capacitors 254 to 258 and inductors 268 and 269 compose the diplexer248.

[0109] Reference numeral 213 a denotes a SAW filter for a DCS reception,and reference numeral 12 b denotes a SAW filter for a PCS reception. Ina DCS reception band (1805-1880 MHz) and PCS reception band (1930-1990MHz), each transmission lines 281 b and 281 c has an electric lengthsetting an impedance from a point F toward the opposite side (i.e.,toward the SAW filter 213 b in the DCS reception band) to anopen-circuit.

[0110] Further, transmission lines 274 and 281 a have electrical lengthsof one-quarter wavelength in the first and third transmission bands,respectively. Therefore both an impedance from a point D toward theright side and an impedance from a point E toward the right side are setto an open-circuit in the first and third transmission bands,respectively.

[0111] In this configuration, a desired operation may be provided.

[0112] The circuit shown in FIG. 11 can be formed in a laminated bodyhaving plural dielectric sheets. At the moment, the diodes 278, 279,290, and 293 and the SAW filters 212, 213 a, and 213 b can be mounted onthe laminated body, and the inductors and capacitors can be formed inthe laminated body. And thus, they can be composed integrally, and havecircuit size much reduced as compared with a flat structure forming thesame circuit on a substrate.

[0113] Incidentally, the circuit composed of inductor 291, capacitor 292and diode 290, and the circuit composed of inductor 294, capacitor 295,and diode 293 may be replaced by one simple inductor only by properlysetting the component values so as to satisfy the individual relationsdescribed above, so that the circuit configuration using only two diodescan be realized.

[0114] According to the embodiment, a hybrid RF switching deviceapplicable to triple bands can be provided, which has a simple circuitconfiguration.

Embodiment 7

[0115] Embodiment 7 of the invention will be explained below byreferring to the drawings. Embodiment 7 shows a one-chip configurationof the hybrid radio frequency (RF) switching device according to theforegoing embodiments 1 to 6.

[0116]FIG. 12 is a perspective view showing a schematic configuration ofa hybrid RF switching device according to embodiment 7 of the invention.Reference numeral 300 denotes a laminated body formed by laminatingplural dielectric sheets each having a relatively low dielectricconstant (about εr<10). In laminated body 300, branching circuits,low-pass filters (LPFs), and a part of switching circuits are formed. Onthe laminated body 300, chip components 302, e.g. diodes, chip inductorsand other, and a surface acoustic wave (SAW) filter 301 are mounted.They compose a one-chip hybrid RF switching module.

[0117] That is, in laminated body 300, inductors for composing circuitsare formed as electrode patterns such as meander patterns or spiralpatterns, and each capacitor is composed of a pair of electrodes. Aninput/output electrode 304 and a ground electrode 303 are formed at theside of the laminated body 300. The SAW filter 301 is mounted on thelaminated body 300 by a wire bonding or flip-chip mounting to reduce thesize.

[0118] The chip components 302, e.g. the diodes for composing switchesand chip inductors used as choke inductors, may not be formed in thelaminated body 300. Even if they can be formed, they have so largevalues that they hardly get small, thus are mounted on the laminatedbody 300. Therefore, elements that cannot be formed in the laminatedbody 300, components having too large values to be reduced in size evenif being formed, and components that is hardly protected against noisemay be mounted on the laminated body 300. That provides a one-chipstructure and reduces the total dimension.

[0119] Although not shown in the diagram, a metal cap groundedelectrically for covering the surface of the laminated body 300 protectsthe module from an external electromagnetic interference. A bare chipand resin-molded chip of the diode can be mounted as a chip component302

[0120] A specific structure of the laminated body 300 will be explainedby referring to FIG. 13.

[0121]FIG. 13 is a perspective exploded view of FIG. 12, in whichreference numerals 300 a to 300 c denote three sheets formed from thebody 300 arbitrarily divided into three, and reference numerals 305 a to305 d denote grounding terminals for mounting the SAW filter 301.Grounding terminals 305 a to 305 d are directly connected to a groundelectrode 303 a formed on sheet 300 c through via-holes 306 a-306 d inthe sheet 300 a and 300 b, respectively. This configuration reduces aparasitic inductance between the ground and each SAW resonators 123 and125 as shown in FIG. 2, and thus decreases a downward shift of aseries-resonance frequency of each SAW resonators 123 and 125. As aresult, the SAW filter 301 has a characteristic in which a frequencyshift of a lower-side attenuation pole decreases, so that adeterioration of an attenuation amount can be reduced.

[0122] Although not shown, the ground electrode 303 a formed close tothe bottom, upon being formed a layer close to the top surface of thelaminated body 300, has the length of each via-holes 306 a-306 dshortened. That decreases the parasitic inductance and the deteriorationof the attenuation amount of the SAW filter 301 more effectively.

[0123] Further, plural via-holes connecting the ground electrode 303 ato each of grounding terminals 305 a to 305 d for the respectivegrounding terminal further decreases the parasitic inductance and thedeterioration of the attenuation amount of the SAW filter 301.

Industrial Applicability

[0124] As clear from the above description, according to the invention,a hybrid radio frequency (RF) switching device including fewer diodesand having a smaller size and a higher performance is provided. Thedevice is sufficiently applicable to multiple bands such as dual bandsand triple bands despite the very simple structure.

1. A hybrid radio frequency (RF) switching device for switching betweena first frequency band and a second frequency being higher than thefirst frequency band, the hybrid radio frequency (RF) switching devicecomprising: first to fourth ports; a diode coupled between the first andsecond ports, a first transmission line having a line length of g/4 n, gbeing a wavelength of a frequency in the first frequency band, n beingan odd number of 1 or larger; a first element coupled between the secondand third ports in series with the first element, the first elementhaving an impedance containing a nearly simple reactance component inthe second frequency band; a second element coupled at a position wherethe first element having a nearly open impedance in the second frequencyband, the second element having an impedance containing a nearly simplereactance component; and one of a reactance circuit and a secondtransmission line, the reactance circuit being coupled in parallel withthe second element, the second transmission line being coupled in serieswith the second element, the second element having an open impedance asseen from a coupling position in the first frequency band.
 2. A hybridRF switching device of claim 1, wherein the first and second elementsinclude surface acoustic wave (SAW) filters.
 3. A hybrid RF switchingdevice of claim 1, wherein the SAW filters include ladder type filtercircuits, respectively.
 4. A hybrid RF switching device of claim 1,wherein each of the ladder type filter circuits includes a SAW waveresonance element at a first stage coupled in shunt between the firsttransmission line and a ground, the SAW filters passing a higherfrequency band of the first frequency band and second frequency band. 5.A hybrid RF switching device of claim 1, wherein the first and/or secondtransmission line includes a concentration constant circuit.
 6. A hybridRF switching device of claim 1, wherein the reactance circuit comprisesa parallel circuit in which an inductor and capacitor are coupled inparallel, wherein the inductor and capacitor parallel-resonate in thesecond frequency band, and wherein the inductor, capacitor, and secondelement resonate in the first frequency band.
 7. A hybrid RF switchingdevice of claim 6, wherein the transmission lines are composed ofmicrostrip lines or strip lines, and the inductor in the reactancecircuit is coupled directly between the transmission lines and theground.
 8. A hybrid RF switching device of claim 1, further comprising acircuit coupled in parallel with the diode, the circuit including: afirst inductor; a second inductor coupled in series with the firstinductor; a capacitor coupled in parallel with the first inductor; and aDC cutting capacitor coupled in series with the first inductor, whereina circuit network including the first inductor, second inductor, andcapacitor parallel-resonate in the first frequency band and secondfrequency band.
 9. A hybrid radio frequency (RF) switching device ofclaim 1, handling a first frequency band, a second frequency band beinghigher than the first frequency band, a third frequency band near thefirst frequency band, and a fourth frequency band near the secondfrequency band, the high frequency composite switch componentcomprising: first to fourth ports; a diode coupled between the first andsecond ports; a first resonance circuit parallel-resonating to have alocal maximum impedance in the first and third frequency bands, andhaving a capacitive impedance in the second frequency band; a firstinductor coupled in shunt between the first resonance circuit and aground; a first capacitor coupled in series with the first resonancecircuit, the first capacitor, first inductor, and first resonancecircuit being coupled in a T-form; a first surface acoustic wave (SAW)filter coupled between the first capacitor and the third port, the firstSAW filter passing the second frequency band; a second resonance circuitparallel-resonating to have a local maximum impedance in the second andfourth frequency bands, and having an inductive impedance in the firstfrequency band; a second capacitor coupled in shunt between the secondresonance circuit and the ground; and a second inductor coupled inseries with the second resonance circuit, the second inductor, secondcapacitor, and second resonance circuit being coupled in a T-form; and asecond SAW filter coupled between the second inductor and the fourthport, the second SAW filter passing the first frequency band; whereinthe first resonance circuit and second resonance circuit are coupled tothe second port through the diode.
 10. A hybrid RF switching device ofclaim 9, wherein the first SAW filter comprises: an input terminalopposite to a side coupled to the third port; and a SAW resonatordisposed at a first stage from the input terminal and coupled to theground in parallel, the SAW resonator series-resonating in the fourthfrequency band.
 11. A hybrid RF switching device of claim 9, wherein thesecond SAW filter comprises: an input terminal opposite to a sidecoupled to the fourth port; and a SAW resonator disposed at a firststage from the input terminal and coupled to the ground in parallel, theSAW resonator series-resonating in the third frequency band.
 12. Ahybrid RF switching device of claim 10, wherein a circuit in which thefirst resonance circuit, the first inductor coupled in shunt between thefirst resonance circuit and the ground, and the first capacitor coupledin series with the first resonance circuit are coupled in the T-form hasan equivalent electric length of λd/4+λd×n in the fourth frequency band,λd being a wavelength in the fourth frequency band, n being an integer).13. A hybrid RF switching device of claim 11, wherein a circuit in whichthe second resonance circuit, the second capacitor coupled in shuntbetween the second resonance circuit and the ground, and the secondinductor coupled in series with the second resonance circuit are coupledin the T-form has an equivalent electric length of λg/4+λg×n in thethird frequency band, λg being a wavelength in the third resonancefrequency, n being an integer.
 14. A hybrid RF switching device 9,wherein a frequency in the second frequency band is about twice afrequency in the first frequency band.
 15. A hybrid RF switching deviceof claim 9, further comprising a circuit coupled in parallel with thediode, the circuit including: a third inductor; a fourth inductorcoupled with the third inductor; a third capacitor coupled in parallelwith the third inductor; and a DC cutting capacitor coupled in serieswith the third inductor, wherein a circuit network having a capacitancebetween terminals of the diode turned off, the third inductor, fourthinductor, and third capacitor parallel-resonates in the first and thirdfrequency bands and the second and fourth frequency bands.
 16. A hybridradio frequency (RF) switching device handling a first frequency band, asecond frequency band being higher than the first frequency band, athird frequency band near the first frequency band, and a fourthfrequency band near the second frequency band, the first and secondfrequency bands being included in a transmission band, the third andfourth frequency bands being included in a reception band, the hybrid RFswitching device comprising: a common port; a switch for switching thetransmission band and the reception band, the switch being coupled at afirst stage from the common port; a first diplexers for dividing thefirst and second frequency bands; a second diplexers for dividing thethird and fourth frequency bands; first and second low-pass filters(LPFs) coupled with the first and second diplexers, respectively, thefirst and second LPFs corresponding the first and second frequencybands, respectively; first and second ports coupled with the first andsecond diplexers through the first and second LPFs, respectively; firstand second surface acoustic wave (SAW) filters coupled with the firstand second diplexers, respectively, the first and second SAW filterspassing the third and fourth frequency bands included in the receptionband, respectively; third and fourth ports coupled with the first andsecond diplexers through the first and second SAW filters, respectively;a laminating body including a dielectric sheet laminated therein,; and adiode included in the switch, wherein the laminating body includes theswitch, first and second diplexers, and first and second LPFs formedtherein, and includes the diode and the first and second SAW filtersmounted thereon.
 17. A hybrid RF switching device of claim 16, wherein afrequency in the second frequency band is about twice a frequency in thefirst frequency band.
 18. A hybrid radio frequency (RF) switching devicehandling a first frequency band, second and third frequency bands closeto each other being higher than the first frequency band, a fourthfrequency band near the first frequency band, and fifth and sixthfrequency bands near the second and third frequency bands, the first,second and third frequency bands being included in a transmission band,the third, fourth, and fifth frequency bands being included in areception band, the hybrid RF switching device comprising: a commonport; a switch for switching the transmission band and the receptionband, the switch being disposed at first from the common port; a firstdiplexer dividing the first, second, and third frequency bands includedin the transmission band; a second diplexer dividing the third, fourth,and fifth frequency bands included in the reception band; a firstlow-pass filter (LPF) corresponding to the first frequency band, beingcoupled with the first diplexer; a first port coupled with the firstdiplexer through the first LPF; a second LPF corresponding commonly tothe second and third frequency bands, being coupled to the seconddiplexer; a second port coupled with the second diplexer through thesecond LPF; first, second, and third surface acoustic wave (SAW) filterspassing the fourth, fifth, and sixth frequency bands included in thereception band, third, fourth and fifth ports coupled with the seconddiplexer through the first, second, and third SAW filters, respectively;a phase shifter for dividing the fifth and sixth frequency bandsdisposed between the second diplexer and the second and third SAWfilters, respectively; a laminated body including a dielectric sheetlaminated therein; and a diode included in the switch, wherein thelaminated body includes the switch, first and second diplexers, firstand second LPFs, and phase shifter formed therein, and includes thediode and first, second and third SAW filters mounted thereon.
 19. Ahybrid RF switching device of claim 18, wherein a frequency in thesecond and third frequency bands is about twice a frequency in the firstfrequency band.
 20. A hybrid RE switching device of claim 16 or 18,further comprising a chip choke composing a part of the switch, the chipchoke inductor being mounted on the laminated body.
 21. A hybrid RFswitching device of claim 16 or 18, further comprising: a groundingelectrode formed in the laminated body; and via holes coupling thegrounding electrode directly with grounding terminals of the SAWfilters, respectively.
 22. A hybrid RF switching device of claim 21,wherein each grounding terminal is directly coupled with the groundingelectrode through a plurality of via holes of the via holes.